1. Technical Field
The present invention relates to a lock-up device, particularly to a lock-up device for a torque converter to transmit torque, and simultaneously, absorb and attenuate torsional vibration.
2. Background Art
In many instances, torque converters include a lock-up device for directly transmitting torque from a front cover to a turbine. The lock-up device includes a piston, a retaining plate, a plurality of pairs of torsion springs, a driven plate, and a support member. The piston can be frictionally coupled to the front cover. The retaining plate is fixed to the piston. The torsion springs are supported by the retaining plate. The driven plate is elastically coupled to the piston through the torsion springs in a rotational direction. The support member is disposed while being rotatable relatively to the piston and the driven plate. It should be noted that the driven plate is herein fixed to the turbine (see Patent Literatures 1 and 2). The piston herein axially divides the space between the front cover and the turbine. Torque of the front cover is configured to be transmitted to the lock-up device when a friction facing annularly attached to the outer peripheral part of the piston is pressed onto a friction surface of the front cover. Accordingly, torque is transmitted from the lock-up device to the turbine. Fluctuation in torque to be inputted from an engine is herein absorbed and attenuated by a plurality of torsion springs disposed in the outer peripheral part of the lock-up device. It should be noted that the plural torsion springs are supported by the support member while a torque converter is thus actuated.
Japan Laid-open Patent Application Publication No. JP-A-2002-089657 (Patent Citation 1) is an example of the related art. Japan Laid-open Patent Application Publication No. JP-A-2008-138797 (Patent Citation 2) is another example of the related art.